ir3500v International Rectifier Corp., ir3500v Datasheet - Page 10

• Manufacturer Part Number: ir3500v
• Description: Xphase3 Vr11.1 Cpu Vtt Control Ic
• Manufacturer: International Rectifier Corp.

This arrangement guarantees the error amplifier is always in control and can demand 0 to 100% duty cycle as
required. It also favors response to a load step decrease which is appropriate given the low output to input voltage
ratio of most systems. The inductor current will increase much more rapidly than decrease in response to load
transients. An additional advantage of the architecture is that differences in ground or input voltage at the phases
have no effect on operation since the PWM ramps are referenced to VDAC. The error amplifier is a high speed
amplifier with 110 dB of open loop gain. It is not unity gain stable. Figure 6 depicts PWM operating waveforms
under various conditions.
PHASE IC
CLOCK
PULSE
PWMRMP
GATEH
GATEL
EAIN
VDAC
Page 10 of 34
STEADY-STATE
OPERATION
DUTY CYCLE INCREASE
DUE TO LOAD
INCREASE
Figure 5 - Frequency variation with ROSC
Figure 6 - PWM Operating Waveforms
DUTY CYCLE DECREASE
DUE TO VIN INCREASE
(FEED-FORWARD)
DUTY CYCLE DECREASE DUE TO LOAD
DECREASE (BODY BRAKING) OR FAULT
(VCC UV, OCP, VID FAULT)
July 03, 2008
IR3500V
STEADY-STATE
OPERATION